Separation film and process



Nov. 17, 1964 D. J. NEWMAN 3,157,547

SEPARATION FILM AND PRocEss Filed April 17. 1961 A Tmp/m6 United States Patent O This invention relates to the preparation of positive or projection transparencies which may be used in contact photoprinting processes, in the projection of light-images, in the control of color values and for other purposes. In one important embodiment, these transparencies are prepared from half-tone printed originais by a process involving a thermal treatment of a novel print-removal film material in contact with the printed original and employing a thermocopying machine.

A suitable copying machine, described in U.S. Patent No. 2,891,165, comprises a print roll and associated transparent belt between which a graphic original and a heatsensitive copy-sheet are held in pressure-contact While the original is briey exposed to intense irradiation. These Thermo-Fax thermocopying machines are available in many oces and other locations and provide high convenient means for the practice of the present invention.

It is frequently found desirable to project representations of printed pictures or other intelligence for purposes of enlargement or for simultaneous viewing by a large audience or for other purposes. Printed material as found in the pages of the so-called slick-paper magazines is particularly important for such use. The originals may be projected by reflection; but unless complex and expensive optical systems are employed, the image is reversed. The original is enclosed within the projector and hence is not accessible for marking during projection. More particularly, the projected image is dim, and cannot be brightened by substitution of more powerful light sources due to the severe heating effects encountered; so that such systems must be used in darkened rooms.

The present invention provides for the separation from the printed page of the inked image as a positive transparency from which a positive image may be obtained by projection, for example by means of an overhead projector. The transparency retains the full color values of the original and permits projection of an image at high light intensity. The projected image is a true reproduction of the printed original. n an overhead projector the transparency is fully accessible for marking by the operator during lectures or demonstrations, and the sheet is receptive of markings applied with wax pencil or analogous marking means.

In the practice of the invention, a heat-activatible adhesive-coated film is first adhered to the printed surface of which a transparency is desired, and which may be a page taken from a slick-paper magazine, by passing the composite, together with a radiation-absorptive heater sheet, through the thermocopying machine. The composite is then treated to release the ink layer and remove any surface fibers or fillers still adhering to the film surface. The ink forming the original design or image remains bonded to the adhesive surface and a positive transparency results. The surface from which the fibrous sheet has just been removed remains rough and semi-translucent, and images obtained by projection through such products lack full clarity and brilliance. It has been found, additionally, that the iilm may be improved in transparency and in addition made non-adherent toward other surfaces, and without any loss of detail'or color separation, by spreading over the inked surface a'thin uniform application of an aqueous dispersion of microparticles of a film-forming non-tacky transparent-resinous polymer.

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In the drawing,

FIGURE l is a partial sectional view illustrating the treatment of the composite of original and separation lm in a Thermo-Fax therrnocopying machine,

FIGURE 2 is a schematic representation in cross section of a portion of the composite during subsequent separation, and

FIGURE 3 is a schematic representation, also in section, of the completed projection transparency.

The apparatus o f FIGURE l is indicated as including a print roll 12, transparent pressure belt 10, and a lamp assembly consisting of a line filament lamp 31 Within a reiiector 32 having a truncated elliptical cross section. Radiation from the lamp is concentrated along a narrow line near the surface of the roller 12 and parallel to its axis. The composite of sheets to be irradiated is passed between the roll 12 andthe belt 1t) in the direction indicated and at constant speed, and is thereby briey irradiated at high intensity. e e

As shown in the figure, the composite consists of inner and outer thin protection sheets 13 and 17 which are transmissive of the heat-producing radiation and which may conveniently be thin dense paper lightly treated with silicone resin. Such treatedpaper is available as protective Wrapping or inter-leaf material. The composite additionaily includes the separation iilm 14, the printed original 15, and preferably a thin radiation-absorptive heater sheetl. The last-namedsheet may be omitted in instances in which the original 15 is itself adequately radiation-absorptive.

Radiation from the lamp 31 is absorbed substantially completely in the heater sheetl and converted to heat which is then conducted to the original i5 andrseparation sheet 14, causing the two to adhere together in the form of a composite 18. This material is next treated to remove the undesired portions of the printed page, as schematically illustrated in connection with FGURE 2. The sheet material is first soaked in an aqueous detergent solution, resulting in a softening of the printed original 15, more particularly at the heavily pigmented and sized printed surface, thus permitting the bulk of the fibrous sheet to be lifted from the inked image here indicated by a series of darkened areas 23. Separation is incomplete, there being numerous fibers and pigmentary deposits 24 remaining attached to the exposed surface. These deposits are then loosened by gentle hand rubbing with a piece of mohair or other soft brush-like material while the sheet is still Wet Vwith the detergent solution. The surface is finally rinsed with clear water and the sheet is dried. Y

Following the washing and drying step, the surface of the separation sheet with the attached ink areas is found to be rough land uneven in character. When placed on the overhead projector and an image projected on the screen, it is found that the image is generaily less bright and less sharp in outline than might bedesired. The

inked surface is next uniformly coated with a thin layer of a resinous latex applied with a saturated sponge, Vand the sheet is again dried. Projections made with the transparency thus treated are found to be sharp in detail, to provide excellent color value, and to be exceptionally brillient in over-all appearance.

FIGURE 3 illustrates in cross section the completed transparency including the-transparent film base 21 and transparent adhesive layer 22 making up the separation film 14%,V the transferred ink areas '23 forming the image, and the transparent surface layer 25. As illustratedrin the figure, the application of the surface layer 2S provides a smooth outer surface, fills all pockets or voids in the inked surface, and insures a direct optical path through the entire structure, without in any wayY disturbing'the position or sharpness of outline of the inked areas 23.

The structure employed 1n the separation film is indicated in FIGURES 2 and 3 as consisting essentiallyo a Y transparent fum backing or carrier 2l and a heat-activati- Vble transparent adhesive layer 22. Although other forlmulations may perhaps be useful under other operating v conditions, it, is found that quite specific requirements Vmust be met when employing the Thermo-Fax thermocopying machine as above described and indicated. The adhesive must be substantially non-tacky at normal room and storge temperature, but must soften quickly, undergoV Example l Partsby weight Viny-acetate homopolymer (Vinylite AYAT) 40 1:1 vinyl stearate:vinyl acetate Vcopolymer (Flex bond B-142.) .2O Vinyl stearate homopolymer (Flexbond D-l08) 20 `Diphenyl phthalate j Y 8 Toluene 1,53 Methylethyl ketone V52 -V The solid components areV dissolved inthe mixture of solvents and-applied in a thin uniform coating to two-mil Y Mylaroriented polyester Iilm, and the coating is dried;V vA dry coatingweight to produce va coating thickness equivalent to that of at least about one gram per square foot of the adhesive is necessary in orderto obtain cornplete removal-of the inked areas from the printed page. Above about grams per square foot the coating shows an increased milkiness or translucency which Vis to be avoidedfand coatings fof Vsuch thicknesses Vare in any ,event unnecessary andeconomically undesirable.

Films ranging from asthn as'about one-half mil up to about 10 mils, Vof Mylar polyester or other transparent water-resistant iilms having adequate handling properties such as ycellulose acetate or copolymer of styrene and acrylonitrile, may alsobe used.

The transparent lm constructed as above indicated yis essentially non-tacky to the touch, but when placed withY the adhesive surface against the printed surface of a pagev of a .slick-paper magazine and the composite passed .a v f i clay, water soluble binder, looseiibers andr other'residual material is then easily loosened by gentle rubbing with a soft brush or brush-like implement and is then rinsed away with clear water.

The cleaned but still wet copy is preferably dried Vbetween absorbent towels to prevent water spotting. The drying may be completed by exposure to moving air at moderately elevated temperature.

The imaged surface is next further transparentized by the application of a thin coating of a film-forming polymer applied in the form of microparticles in aqueous dispersion. A preferred material is Darex Polymer Y, a polyvinyliacetate copolymer colloidal latex containing '50% solids, the polymer having a molecular weight of abouti-4,090 and forming a hard and non-tacky s`elfV sustainingiilm when the latex is dried in tilm form. Another ksuitable material is Everiiex MC-400 vinyl acetate/ethyl acrylate copolymer colloidal emulsion which on drying forms transparentrand non-tacky but somewhatV softer dried film. V-

Whereas the dried transparency as initially formed shows considerable tendency to stick to surfaces with which in contact at room or moderately elevated tempera-KY Y tures, the product after the application of thepolymer latexexhibits no such tendency. Although the microparticles ofthe polymer become firmly attached to the surface of the transparency and blend together to form a smooth clear'surface layer, they have no visible effect on the inked image either `at the larger inked areas or even at the finest half-tone dots. Colorsparation in the transparency thus remains fully equal to whatV was available in the original printed page. The'brilliance ofthe projected imagel is signiiicantly increased, making possible the effective projection from such transparencies under conditions of full, room illumination. l

The separation of printedimages simultaneously from both surfaces of a magazine page or other printed original may. be'accomplished by Yanalogous procedures by colloidally dispersed resin as already described.

through vthetherrnocopying machine as hereinbefore in- V- i dicated, the-adhesive is softened sufficiently so that, under the pressure contact applied in the machine, it attains fullV and complete adhesion to the ink pattern throughout its entire area. All Vof the half-tone dots ofpictured illustrations as Well as the solid areas of printed letters and the like are eiectively bonded to the adhesive coating. V The adhesive vadditionally forms a bond to the clay-coated and fibrous-'surface of the Ybackground areas of the printed page, which bond must accordingly be subsequently-brok- Venfto permit Yseparation andisolationof the linked image.

This separation is achieved, as previously noted, by

brief soaking orthe entireV composite in water at'V room Y temperature and towhich has been added small amounts of detergent lorfvvetting agent.y f AnyV of the commercially available detergents are YVeffective, such as those based on l Ysulfated alcohols, sodiumlauryl sulfate or others; and the concentration is inno-way: critical.- These may be further compoundedwith trisodiumV phosphate or similar modifiers or builders. jOne lcommerciallyavailable prod- ;x uct is Spick-n-Spanfaf proprietary blend' of 20 parts of Y' trisodium phosphate'jgparts of dodecyl Vbenzene sulfonate, and L'Zl parts of inert additive.

Ag Within oneor two'rninutes Vthe paper absorbsythe solution and the clay'coating is softened and weakened to such j anextent that the fibrous backing may'beoated or lifted 'Y 'Y jawayfwithout diiiculty. The remaining thinecoating of merely increasing the soaking time in the detergentsolu.- tion. Each of the two resulting -transparencies is then scrubbed, rinsed, dried, and brightenedby applicationo The specific adhesive formula provided inthe example has given excellent results under the conditions described and is preferred, vbut' slight modificationsv and variations may be'made without significant loss of'properties. As

an example, the amount of any one of theV four solid components may be varied within the limits of about onehalf to about twice the amount-indicated in the formula;

and corresponding variations may be made in two'orV more of the components providing the changes are not exces-VV rsive. f @Y The process as hereinbefore,describedV permits Vthey Y preparation of projection transparenciesofrom magazine i pages or analogous sources so that graphic subject matter of all types may be easily and rapidly prepared for directV viewing or for lprojection.v The same transparencies fareY equally useful in contact printing, for example in prepar ing multiple copies of the subject matter on diazo or other light-,sensitive copy-papers.

The process of-makingA transparencies as herein de,Y

scribed has a'dditio'nalutilityV in the color printing industry in preparing proofs of color separations. Such proofs are particularly useful in assessing, the color values of the Vparticular printing inks employed.V The process involvesV printing each monocolor Vimage -on jdecalcomania base 1' stock, slick-paper, or other transfer-sheet, preparing a `separation"transparencyfrom'each ofthe printed monocolor images by procedures hereinbefore described, and Y thenY placing Ythe lseveral transparencies "in Vregister 'andf comparing the resulting'colored image with the colored original fromwhiehthe separations were prepared. -Any differences inthe inks employedrin printingV the separateY Y colors will'thus beV made Vimrrlediately apparent and can be corrected, and again tested by way of ya further set of Yseparation transparencies. l

nal; (b) soaking the adherently bonded original and film in aqueous detergent solution to soften the transfer paper surface; (c) removing the paper and any residual nonimage areas thereof from said film; and (d) applying to the exposed roughened print-carrying surface of said film a thin coating of resinous film-forming, vinyl copolymer aqueous latex and drying the coating, to clarify and protect the said surface.

2. The process of claim 1 in which the separation film comprises a thin exible transparent iilm backing and a thin smooth coating thereon of a transparent heat-activatible normally lirm and non-tacky adhesive which becomes aggressively tacky on being heated to an activation temperature within the range of about 60-120 C. and which consists essentially, in parts by Weight, of vinyl acetate honiopolymer about 20-60 parts; copolymer of 3 parts vinyl stearate and 1 part vinyl acetate, about 10-30 parts; vinyl stearate homopolymer, about -30 parts; and diphenyl phthalate about 4-12 parts.

3. A color separation sheet adapted for the preparation of clear and accurate projection transparencies from printed originals by brief moderate heating in pressure conatct With such original all as herein described, said sheet comprising a thin, flexible Water-resistant transparent iilm backing and a normally non-tacky uniform surface layer of about 1-5 grams per square foot of a heat-activatible adhesive composition consisting essentially, in parts by weight, of vinyl acetate homopolymer about 20-60 parts; copolymer of 3 parts Vinyl stearate and 1 part vinyl acetate, about 10-30 parts; vinyl stearate homopolymer, about 10-30 parts; and diphenyl phthalate about 4-12 parts.

4. A color separation sheet adapted for the preparation of clear and accurate projection transparencies from printed originals by brief moderate heating in pressure contact with such original all as herein described, said sheet comprising a thin, flexible Water-resistant tarnsparent film backing and a normally non-tacky uniform surface layer of about 1-5 grams per square foot of a heatactivatible adhesive composition consisting essentially, in parts by Weight, of vinyl acetate homopolymer about parts; copolymer of 3 parts vinyl stearate and 1 part vinyl acetate, about 20 parts; vinyl stearate hornopolymer, about 20 parts; and diphenyl phthalate about 8 parts.

5. A heat-activatible transparent adhesive composition useful in the form of a thin surface coating on a thin flexible transparent film backing as a separation film for the preparation of separation transparencies as herein described, said adhesive consisting essentially, in parts by Weight, of vinyl acetate homopolymer about 20-60 parts; copolymer of 3 parts vinyl stearato and 1 part vinyl acetate, about 10-30 parts; vinyl stearate homopolymer, about 10-30 parts; and diphenyl phthalate about 4-12 parts.

References Cited in the file of this patent UNITED STATES PATENTS 2,101,876 Scott Dec. 14, 1937 2,154,474 cott Apr. 18, 1939 2,431,078 Powell et al. NOV. 18, 1947 2,432,484 Moulton Dec. 9, 1947 2,489,987 Barnola Nov. 29, 1949 2,556,078 Francis June 5, 1951 2,559,790 Peters July 10, 1951 2,643,238 Crozier et al. June 23, 1953 

1. PROCESS FOR THE PREPARATION OF A CLEAR AND SHARP PROJECTION TRANSPARENCY FROM A PRINTED ORIGINAL WHICH COMPRISES THE STEPS OF (A) BRIEFLY EXPOSING TO INTENSE RADIATION UNDER MODERATE PRESSURE A COMPOSITE OF THIN FLEXIBLE SHEET MATERIALS COMPRISING, IN ORDER, A FIRST THHIN PROTECTIVE WEB, A RADIATION-/ABSORPTIVE HEATER SHEET, AN ORIGINAL PRINTED ON TRNSFER PAPER, A HEAT-ACTIVATABLE ADHESIVE SEPARATION FILM, AND A SECOND THIN PROTECTIVE WEB, TO CAUSE BRIEF MODERATE HEATING OF SAID COMPOSITE AND BONDING OF SAID FILM TO THE PRINTED SURFACE OF SAID ORGINAL; (B) SOAKING THE ADHERENTLY BONDED ORIGINAL AND FILM IN AQUEOUS DETERGENT SOLUTION TO SOFTEN THE TRANSFER PAPER SURFACE; (C) REMOVING THE PAPER AND ANY RESIDUAL NONIMAGE AREAS THEREOF FROM SAID FILM; AND (D) APPLYING TO THE EXPOSED ROUGHENED PRINT-CARRYING SURFACE OF SAID FILM A THIN COATING OF RESINOUS FILM-FORMING, VINYL COPOLYMER AQUEOUS LATEX AND DRYING THE COATING, TO CLARIFY AND PROTECT THE SAID SURFACE. 